I have a "friend" who seems to really enjoy figuratively spitting on his other friends' attempts at political activism. So, for example, if you go out and do political activity A, he will roll his eyes and say, why are you doing A, when B and C are the real problems? As though it is possible to do only one thing. Even though many of us are doing A, B, C, D, and anything else we can think of.
So, what is the logical fallacy that he is employing here?